Fig. l. Copied from a sketch by Mr. Sopwith, of the base of a large trunk of Sigillaria standing in 1803, in the cliff at Bog Hall, near Newbiggin, on the [091] coast of Northumberland. This fragment is about five feet high, and two feet three inches in diameter at its base.* Scale one-twenty-fourth. (Sopwith.)

2. Fragment of the bark on the trunk of a Sigillaria, from Earl Fitzwilliam's coal mine at Elsecar, near Rotherham. In this mine many large trunks are seen inclined in all directions, and some nearly vertical. (See V. I. p. 470, Note.) The bark is converted into a thin lamina of coal, and remains attached to the lower portion of this specimen. It exhibits on its outer surface scars formed by the articulations of the bases of leaves; these are penetrated near their centre by three apertures for vessels that passed from each leaf into the trunk. The decorticated upper part of this specimen presents an impression of its striated internal surface, and exhibits beneath each scale two oblong parallel apertures, through which the vessels from a leaf penetrated the trunk. Scale one-half. (Original.)

The substance of the trunk must have been in a state of decay, before the mud, which is now hardened into shale, could have entered the interior of the bark. When trunks of this kind are inclined at an angle exceeding 45°, they are usually distended with sandstone, or sandy shale; when at a less angle than 45°, they are most commonly compressed, and have only a thin flat portion of shale, formed of indurated mud within their bark. The bark, wherever it has not perished, is converted to coal.

* M. Ad. Brongniart found a stem of Sigillaria in a coal mine at Essen in Westphalia, which was dichotomous near its top.

2'. Articulating leaf-scar on the exterior of the bark of another large trunk of Sigillaria from Elsecar. Nat. [092] size. On comparing this scar with those upon the bark of Fig. 2, it may be seen that the different modes of articulation of the leaves with the cortical integument present obvious characters, on which specific distinctions may perhaps most easily be established, in this very obscure and curious family of extinct plants. See various figures of these leaf-scars in Lindley and Hutton's Fossil Flora, Plates 55. 56. 57. 71. 72. &c. In Figs. 2, and 2', as in many other species, decurrent lines are visible on both sides of the scar. (Original.)

Fig. 3. Ulodendron Allanii, (nobis) scale one-fifth. See V. I. p. 475. Note. Drawn from a plaster cast of an impression on sandstone, in the Museum of the Royal Society of Edinburgh from the Coal formation at Craigleith This sandstone has formed a natural mould on the outer surface of a stem, which has entirely perished; our cast gives a facsimile of the small rhomboidal scales, and of three large round scars on the exterior of the trunk. This impression has been figured, in an inverted position, by Mr. Allan in Vol. IX. Trans. Royal Soc. Edin. 1823. Pl. XIV. p. 236. (Original.)

Our figure represents the trunk in its natural position. In the centre of each scar is a cavity, indicating the place of attachment of a cone. The upper portion of each scar is marked with furrows, produced by pressure of the long radiating scales at the bottom of the cone. This pressure has nearly obliterated the smaller rhomboidal scales of the bark, in those parts where the furrows are deepest; on the lower portion of the scars, the scales of the bark have been but slightly modified by pressure of the cone. [093]

Fig. 4. A single scar formed by the attachment of a cone of another species, Ulodendron Lucasii, (nobis) discovered by Mr. Lucas in the S. Wales Coal field near Swansea. Some scales and speared-shaped leaves of the trunk are still preserved around the margin of this scar. As the bark has fallen off; we have only the impression of its inner surface. This surface exhibits small apertures, through which vessels entered from beneath the bark-scales into the trunk. On the upper part of the disk, the traces of many of these vessels have been obliterated by pressure of the cone. Scale one-fourth. (Original.)

Fig. 5. Ulodendron Stokesii. (nobis) A large oval scar, (4 1/4 inches in its longer, and 3 1/2 inches in its shorter diameter) preserved in shale from an unknown locality in the English Coal Formation. On the margin of this scar are the remains of rhomboidal scales, and impressions of scales, and a few small leaves. Within the disk a few fragments only of the bark remain near its upper margin. Near its centre, is the mark of the insertion of the stem of a large cone. The lower half exhibits a series of small tubular cavities, marking the place of vessels which passed from the bark into the trunk, one beneath each of the bark-scales that have fallen off. In the upper half of the Scar, there are but slight traces of these cavities, and the surface is marked with furrows, produced by pressure of the long radiating scales of the base of the cone. Scale one fifth. (Original.)

Fig. 6. Ulodendron Rhodji. (nobis) Scar on a scaly stem, from the Coal field of Silesia, figured by Rhode in his Beitrage zur Pflanzenkunde der Vorwelt, L. 2. Pl. 3. Fig. l. The lower portion of this Scar [094] retains the bark-scales modified by pressure of the Strobilus or cone that grew from the centre of the disk. The upper portion of the Scar is without indications of bark-scales, and is covered with radiating furrows, impressed on it by the long slender scales of the base of the Strobilus, which have obliterated the bark-scales.*

The character of this scar approaches to that of Fig. 5, but its proportions differ, measuring 3 1/4 inches in the longer, and 2 1/2 inches in the shorter diameter. The scaly bark (which in Fig. 5 has been almost entirely removed from the area of the scar), is preserved on the lower portion of the disk of Fig. 6. Scale two-ninths. (Original.)

Fig. 6'. Cast of Ulodendron Conybearii (nobis) formed by Pennant sandstone of the Coal formation at Stapleton near Bristol. This cast expresses the exact form of an oval scar, or cavity on a stein from which a cone had fallen off.

The disk is covered with slight ridges and furrows, radiating in all directions from the point of insertion of the cone, and formed by pressure of its lowest scales upon the portion of the stem to which it was attached. Beneath the point of insertion, a [095] few small scales of the bark remain adhering to the Sandstone. Scale one-fourth. (Original.)

* The portions above and below the line drawn across Fig. 6, are copied from two scars in Rhode's figure. Rhode considers these impressions to be flowers, and the compressed bark-scales to be the Petioles of the flower, and has represented the trunk in an inverted position.

As, in every species of Ulodendron which we have seen, the furrows produced by scales at the base of the cone, are deepest on the upper portion of the Scar, we infer from this circumstance that the cones were inclined upwards and inwards, with their axis apprximating to that of the stem from which they issued.
 

Fig. 7. Portion of the trunk of Favularia, one-fourth nat. size. This plant is distinguished by the tessellated appearance of the scales, which cover the space between each fluting of the Bark. In the centre of the area of each scale is a club-shaped scar, which gave origin to a leaf; it was a dicotyledonous plant, probably allied to Sigillaria; and its stem must have been covered with a mass of densely imbricated foliage. In the Genus Sigillaria the leaves were more distant. from one another. The Rows of scars are separated by a groove, Fig. 7. 6.; their disposition in the vertical direction is indicated by the line a. (Lindley, Foss. Fl. Pl. 73.)

Fig. 8. Reduced from Lindley and Hutton's figure (Pl. 31) of the central portion of a Stigmaria ficoides, from Shale in the roof of the Jarrow colliery near Newcastle. We have here a view of the inferior surface of this curious plant. Its dome-shaped hollow central trunk, or stem, was three feet in diameter, and fitted to sustain horizontally in a floating position the numerous long branches by which it was surrounded; these divide into two, at a certain distance from the Trunk. When perfect, and floating in water, its appearance must have resembled the form of an Asterias. On the two longest branches, a. b. is seen the longitudinal depression, which is usually adjacent to the small internal woody axis of these branches, and from its position in this fossil, we learn that the place of this depression was on the interior surface of each branch. Scale one-twenty-fourth. (See V. I. p. 476.) [096]

Fig. 9. Vertical section of the dome-shaped trunk of Stigmaria, shewing the relative position of the branches. (Lindley and Hutton.)

Fig. 10. Restored portion of a branch of Stigmaria, shewing the manner in which the long cylindrical leaves proceeded from the tubercles around its surface to the length of many feet. In front, extending from a. to b. is seen the depression adjacent to the internal eccentric woody axis a. From b. to c. this axis is laid bare by the removal of a portion of the sandstone. This part of the axis is drawn from a specimen in the Oxford Museum. Scale one seventh. (Original.)

Fig. 11. Fragment of a branch of Stiginaria, shewing the character of the Tubercles, which formed articulations with the bases of the leaves. The enlargement of the leaf towards its base (a) seems to have been calculated to strengthen this part, and to afford space for the articulating socket. This socket formed, with the spherical tubercle, an universal ball and socket joint, admitting of motion in every direction to a long cylindrical leaf floating in water. Scale one-half. (Steinberg.)